Volvo Penta outboard racing

The boat in the image is a custom-built tunnel hull racer from 1975–1977, developed as part of Volvo Penta's factory-backed outboard racing program to promote their performance marine line

During these specific years, Volvo Penta's official factory squad was piloted by top-tier international racing drivers including Paris Saxon, Ove Torkildsen, Lasse Ström, and Gert Lowisin, frequently testing and competing on open waters across Torsby and Uppsala in Sweden, as well as the treacherous circuits in Norway.

The boat is fitted with a specialized racing engine code-named GTX 500 - a 500cc variant built in partnership with iconic German racing engineer Dieter König.

This powertrain relied on distinct fiberglass-reinforced rotary valves and dual carburetors designed specifically to output high power at high RPMs to beat dominate Mercury and OMC (Evinrude/Johnson) outboards.
Source: classicboatracing.se